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Encoding.GetCharCount Method (Byte[], Int32, Int32)

When overridden in a derived class, calculates the number of characters produced by decoding a sequence of bytes from the specified byte array.

Namespace:  System.Text
Assembly:  mscorlib (in mscorlib.dll)

public abstract int GetCharCount(
	byte[] bytes,
	int index,
	int count
)

Parameters

bytes
Type: System.Byte[]
The byte array containing the sequence of bytes to decode.
index
Type: System.Int32
The zero-based index of the first byte to decode.
count
Type: System.Int32
The number of bytes to decode.

Return Value

Type: System.Int32
The number of characters produced by decoding the specified sequence of bytes.

ExceptionCondition
ArgumentNullException

bytes is null.

ArgumentOutOfRangeException

index or count is less than zero.

-or-

index and count do not denote a valid range in bytes.

DecoderFallbackException

A fallback occurred (see Understanding Encodings for complete explanation).

To calculate the exact array size required by GetChars to store the resulting characters, the application should use GetCharCount. To calculate the maximum array size, the application should use GetMaxCharCount. The GetCharCount method generally allocates less memory, while the GetMaxCharCount method generally executes faster.

For a discussion of programming considerations for use of this method, see the Encoding class description.

The following code example converts a string from one encoding to another.


using System;
using System.Text;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string unicodeString = "This string contains the unicode character Pi (\u03a0)";

      // Create two different encodings.
      Encoding utf8 = Encoding.UTF8;
      Encoding unicode = Encoding.Unicode;

      // Convert the string into a byte[].
      byte[] unicodeBytes = unicode.GetBytes(unicodeString);

      // Perform the conversion from one encoding to the other.
      byte[] utf8Bytes = Encoding.Convert(unicode, utf8, unicodeBytes);

      // Convert the new byte[] into a char[] and then into a string.
      char[] utf8Chars = new char[utf8.GetCharCount(utf8Bytes, 0, utf8Bytes.Length)];
      utf8.GetChars(utf8Bytes, 0, utf8Bytes.Length, utf8Chars, 0);
      string utf8String = new string(utf8Chars);

      // Display the strings created before and after the conversion.
      outputBlock.Text += String.Format("Original string: {0}", unicodeString) + "\n";
      outputBlock.Text += String.Format("Ascii converted string: {0}", utf8String) + "\n";
   }
}
// The example displays the following output:
//    Original string: This string contains the unicode character Pi (Π)
//    Ascii converted string: This string contains the unicode character Pi (?)


The following code example encodes a string into an array of bytes, and then decodes a range of the bytes into an array of characters.


using System;
using System.Text;

public class Example
{

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      // Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      Encoding u32LE = Encoding.GetEncoding("utf-32");
      Encoding u32BE = Encoding.GetEncoding("utf-32BE");

      // Use a string containing the following characters:
      //    Latin Small Letter Z (U+007A)
      //    Latin Small Letter A (U+0061)
      //    Combining Breve (U+0306)
      //    Latin Small Letter AE With Acute (U+01FD)
      //    Greek Small Letter Beta (U+03B2)
      String myStr = "za\u0306\u01FD\u03B2";

      // Encode the string using the big-endian byte order.
      byte[] barrBE = new byte[u32BE.GetByteCount(myStr)];
      u32BE.GetBytes(myStr, 0, myStr.Length, barrBE, 0);

      // Encode the string using the little-endian byte order.
      byte[] barrLE = new byte[u32LE.GetByteCount(myStr)];
      u32LE.GetBytes(myStr, 0, myStr.Length, barrLE, 0);

      // Get the char counts, decode eight bytes starting at index 0,
      // and print out the counts and the resulting bytes.
      outputBlock.Text += "BE array with BE encoding : ";
      PrintCountsAndChars(outputBlock, barrBE, 0, 8, u32BE);
      outputBlock.Text += "LE array with LE encoding : ";
      PrintCountsAndChars(outputBlock, barrLE, 0, 8, u32LE);

   }


   public static void PrintCountsAndChars(System.Windows.Controls.TextBlock outputBlock, byte[] bytes, int index, int count, Encoding enc)
   {

      // Display the name of the encoding used.
      outputBlock.Text += String.Format("{0,-25} :", enc.ToString());

      // Display the exact character count.
      int iCC = enc.GetCharCount(bytes, index, count);
      outputBlock.Text += String.Format(" {0,-3}", iCC);

      // Display the maximum character count.
      int iMCC = enc.GetMaxCharCount(count);
      outputBlock.Text += String.Format(" {0,-3} :", iMCC);

      // Decode the bytes and display the characters.
      char[] chars = enc.GetChars(bytes, index, count);

      // The following is an alternative way to decode the bytes:
      // char[] chars = new char[iCC];
      // enc.GetChars( bytes, index, count, chars, 0 );

      outputBlock.Text += chars + "\n";

   }

}


/* 
This code produces the following output.  The question marks take the place of characters that cannot be displayed at the console.

BE array with BE encoding : System.Text.UTF32Encoding : 2   6   :za
LE array with LE encoding : System.Text.UTF32Encoding : 2   6   :za

*/



Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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